An important for goal for agriculture is to produce plants with agronomically important traits. Recent advances in genetic manipulation provide the tools to transform plants to contain and express foreign genes. This has led to the development of plants capable of expressing pharmaceuticals and other chemicals, plants with increased pest resistance, increased stress tolerance and many other beneficial traits.
It is often desirable to control expression of a polynucleotide of interest, in a particular tissue, at a particular developmental stage, or under particular conditions, in which the polynucleotide is not normally expressed. The polynucleotide of interest may encode a protein or alternatively may be intended to effect silencing of a corresponding target gene.
Plant promoter sequences are useful in genetic manipulation for directing such spatial, temporal and inducible expression of polynucleotides in transgenic plants. To achieve this, a genetic construct is often introduced into a plant cell or plant. Typically such constructs include a plant promoter operably linked to the polynucleotide sequence of interest. Such a promoter need not normally be associated with the gene of interest. Once transformed, the promoter controls expression of the operably linked polynucleotide of interest thus leading to the desired transgene expression and resulting desired phenotypic characteristics in the plant.
Promoters used in genetic manipulation are typically derived from the 5′ un-transcribed region of genes and contain regulatory elements that are necessary to control expression of the operably linked polynucleotide. Promoters useful for plant biotechnology can be classified depending on when and where they direct expression. For example promoters may be tissue specific or constitutive (capable of transcribing sequences in multiple tissues). Other classes of promoters include inducible promoters that can be triggered on external stimuli such as environmental, and chemical stimuli.
It would be beneficial to have a variety of promoters available in order to ensure that transgenes are transcribed efficiently in the right tissues, at an appropriate stage of growth or development. Additionally it may be desirable to direct a gene expression in response to certain environmental or chemicals signals.
Promoters that are responsive to stresses, including mechanical and environmental stresses may be of particular benefit. It has been shown that constitutive expression of stress-inducible genes has negative impact on plant growth and development in the absence of the stress (Kasuga et al. 1999 Nature Biotechnology 17:287-291). Stress responsive promoters may therefore be particularly useful for driving expression of stress-inducible or stress-protective genes. If such genes are linked to a stress responsive promoter such genes are only induced under the appropriate stress conditions.
Perennial ryegrass (Lolium perenne L) is the major grass species grown in New Zealand and other temperate climates throughout the world. Valuable traits that may be improved by genetic manipulation of perennial ryegrass include stress tolerance, disease tolerance and nutritional quality. Genetic manipulation of such traits in perennial ryegrass is limited by the availability of promoters, particularly stress-responsive promoters, capable of appropriately controlling the expression of genes of interest.
It is therefore an object of the present invention to provide a stress responsive promoter from ryegrass useful for controlling expression of genes in plants or at least to provide a useful choice.